de·form /dɪˈfɔːm $ -ɔːrm/ verb [intransitiveI, transitiveT] deform• The disease often causes joints to deform.• Naturally we have to add the proviso that the whole series has not been deformed and completely overturned at some later time.• Trees and hedges have been deformed by the fierce salt spray and strong sea winds during winter.• He did join, hoping to reform the church before it deformed him.• I agree with Leonard Woolf that to write against a weekly deadline deforms the brain.